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DragonFly users List (threaded) for 2004-11
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Re: compiling-optimizing dfly

From: Joerg Sonnenberger <joerg@xxxxxxxxxxxxxxxxx>
Date: Sat, 27 Nov 2004 16:48:45 +0100

On Sat, Nov 27, 2004 at 10:41:27AM +0700, Budhi Setiawan wrote:
> can we compiling & optimizing dfly with best FLAGS,
> ex : with -march=some_arch -O3 -pipe -fomit-frame-pointer

You can set CPUTYPE via environment or /etc/make.conf. Be warned that
e.g. CPUTYPE=p4 and CCVER=gcc2 (the default) can and most likely does
create bad code. There are some known problems with CCVER=gcc34 in
the boot loader, but the normal system should work.
-fomit-frame-pointer makes debugging hard, but is otherwise safe from
the optimizer point. -O3 should *not* be used. We don't support anything
beyond -O1 and for some parts -Os too, but it is difficult to verify
some assumptions of the old code base and there are lots of GCC bugs
triggered by -O3.

To summarize, entries like the following in /etc/make.conf most
likely works:
CCVER = gcc34	# test boot loader, use the old version if this fails
CPUTYPE=p3	# optimizing for p3, p4 is riskly [not sure of bugfixes]

The speed difference for kernel and normal userland should be neglectable,
compared to higher optimizer settings.


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